Wireless mobile communication systems up to fourth generation transmit and receive control channel and data based on an isotropic or omnidirectional antenna in a frequency band below 1 GHz or between 1˜3 GHz. The wireless mobile communication system may support a selective function for allocating some resources to a user who meets a particular channel condition, through digital beamforming. A cellular system conducts research on an additional performance gain by applying a transmit (Tx) diversity and a receive (Rx) diversity such as multipath propagation which naturally generates according to channel characteristics and Multiple Input Multiple Output (MIMO) using multiple transmit/receive antennas.
By contrast, in an ultrahigh frequency such as millimeter wave, the channel characteristics and Tx/Rx beamforming can obtain a beamforming gain by mitigating the channel multipath propagation, but it is difficult to support the Tx/Rx diversity. Hence, researches are limited mostly to a beamforming weight coefficient which optimizes a performance index such as receive Signal-to-Noise Ratio (SNR) by maximizing the beamforming gain when the beamforming is applied. The related art operates the beamforming with an analog array including a plurality of Radio Frequency (RF)/antenna elements based on a single RF path, without supporting the MIMO. In so doing, the beamforming is operated by sweeping a particular beam pattern in several directions and selecting and feeding back one beam of the strongest receive signal in a receiving stage. This is applicable to an indoor environment having Light of Sight (LoS) as a channel path in a proximity distance within several meters without mobility.
In the outdoor wireless communication which is subject to abrupt channel condition change caused by the mobility of tens of km/h, fast rotation of a terminal, or Non-Line-of-Sight (NLos) path characteristics or channel fading due to an obstacle, when the beamforming gain is maximized in a particular direction and the beamforming of narrow bandwidth is operated with directivity, sensitivity can increase due to the considerable performance degradation according to the user environment. By use of the beamforming as discussed above, the wireless communication system can optimize the performance index such as receive SNR by maximizing the beamforming gain.
However, the wireless communication system using the beamforming cannot obtain the diversity gain because the multipath propagation reduces. The terminal mobility or the channel condition and beamforming information mismatch caused by delay until actual beam allocation after the beam is measured/selected can make the performance sensitive to the beamforming. That is, the ultrahigh frequency wireless mobile communication system based on the beamforming is sensitive to the channel fading and the obstacle because of a great propagation loss and a great penetration loss caused by the channel propagation of the ultrahigh frequency band, the small multipath propagation, and strong directivity caused by the beamforming.
Hence, a system may be designed on the assumption that one or more beam patterns having different beamwidths and gains are operated differently by considering the channel condition or the resource characteristics between the data channel and the control channel with different coding gains, between an uplink and a downlink (or between the transmission and the reception), or between a broadcast channel and a unicast channel.
However, when the beam patterns of the different beamwidths and gains are operated, the beamforming gain difference arises in a particular direction according to the trade-off between the beamwidth and the beamforming gain according to the beam patterns.